Over-voltage protection circuit

ABSTRACT

A network device comprising an integrated circuit configured for coupling to lines between a network connector and an Ethernet physical layer (PHY) and comprising a diode bridge and protection circuitry integrated onto a common integrated circuit whereby parasitics in an energy discharge path and stress on the PHY and the diode bridge are reduced.

BACKGROUND

Many networks such as local and wide area networks (LAN/WAN) structures are used to carry and distribute data communication signals between devices. Various network elements include hubs, switches, routers, and bridges, peripheral devices, such as, but not limited to, printers, data servers, desktop personal computers (PCs), portable PCs and personal data assistants (PDAs) equipped with network interface cards. Devices that connect to the network structure use power to enable operation. Power of the devices may be supplied by either an internal or an external power supply such as batteries or an AC power via a connection to an electrical outlet.

Some network solutions can distribute power over the network in combination with data communications. Power distribution over a network consolidates power and data communications over a single network connection to reduce installation costs, ensures power to network elements in the event of a traditional power failure, and enables reduction in the number of power cables, AC to DC adapters, and/or AC power supplies which may create fire and physical hazards. Additionally, power distributed over a network such as an Ethernet network may function as an uninterruptible power supply (UPS) to components or devices that normally would be powered using a dedicated UPS.

Additionally, network appliances, for example voice-over-Internet-Protocol (VOIP) telephones and other devices, are increasingly deployed and consume power. When compared to traditional counterparts, network appliances use an additional power feed. One drawback of VOIP telephony is that in the event of a power failure the ability to contact emergency services via an independently powered telephone is removed. The ability to distribute power to network appliances or circuits enable network appliances such as a VOIP telephone to operate in a fashion similar to ordinary analog telephone networks currently in use.

Distribution of power over Ethernet (PoE) network connections is in part governed by the Institute of Electrical and Electronics Engineers (IEEE) Standard 802.3 and other relevant standards, standards that are incorporated herein by reference. However, power distribution schemes within a network environment typically employ cumbersome, real estate intensive, magnetic transformers. Additionally, power-over-Ethernet (PoE) specifications under the IEEE 802.3 standard are stringent and often limit allowable power.

Silicon-based electronic devices are susceptible to damage from spurious events that exert voltage/current stresses exceeding the normal operating limits of the devices.

Stress events can be surges on the power line originating from causes such as lightning strikes, but can also originate from human body discharge. If the stress event lasts sufficiently long or the spike in voltage is sufficiently severe, momentary current along a temporary path through the substrate can cause failure through overheating, which causes the silicon or metal to reach the melting point. Lighting and electro-static discharge (ESD) events can be very fast, with time constants as short as 6 ns. The maximum voltage overstress during an event is typically determined by the reaction time of protection devices so that small parasitic changes can cause large variations in the magnitude of overstress.

In Power-over-Ethernet (PoE) applications a powered device (PD) physical interface (PHY) is particularly vulnerable. Although the PHY will unavoidably absorb part of the resulting surge, the function of the protection circuitry is to make the absorbed energy as small as possible by diverting most of the energy through the protection circuitry. Typical designs are intended to ensure that the energy dissipated in the PHY is lower than the energy of a strike as defined by International Electrotechnical Commission (IEC) standard 61000-4-2.

In some cases power is not available through the Ethernet line, so the PD is powered locally, for example through an AC adapter. Local powering of the PD presents substantial risk because the path to earth ground is more direct than when the device is powered through the Ethernet line, allowing a higher current and therefore a higher thermal energy level to dissipate.

To avoid damage, the protective circuitry must respond to a strike within a limited time frame, forming a relatively large current path through the protective circuits and dissipating a significant amount of thermal energy without being destroyed during the surge. High current has to be discharged through a low impedance path, thereby avoiding development of voltages that exceed component specifications. In addition, the protective circuitry must reset sufficiently quickly to respond to subsequent strikes as soon as the strikes are likely to occur.

SUMMARY

According to an embodiment of a network device, an integrated circuit configured for coupling to lines between a network connector and an Ethernet physical layer (PHY) comprises a diode bridge and protection circuitry integrated onto a common integrated circuit whereby parasitics in an energy discharge path and stress on the PHY and the diode bridge are reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention relating to both structure and method of operation may best be understood by referring to the following description and accompanying drawings:

FIGS. 1A and 1B are schematic block diagrams that respectively illustrate a high level example embodiments of client devices in which power is supplied separately to network attached client devices, and a switch that is a power supply equipment (PSE)-capable power-over Ethernet (PoE) enabled LAN switch that supplies both data and power signals to the client devices;

FIG. 2 is a functional block diagram illustrating a network interface including a network powered device (PD) interface and a network power supply equipment (PSE) interface, each implementing a non-magnetic transformer and choke circuitry;

FIG. 3A is a schematic block diagram that shows an embodiment of a network device comprising an integrated rectification and protection system;

FIG. 3B is a schematic block diagram illustrating an embodiment of a network device with an integrated rectification and protection system adapted for usage with a T-Less Connect™ solid-state transformer;

FIGS. 4A and 4B are schematic flow charts depict embodiments of a method for rectification and surge protection in a Power-over-Ethernet application;

FIG. 5 is a schematic block and circuit diagram illustrating a non-integrated rectification and protection circuit;

FIGS. 6A, 6B, and 6C are graphs showing over-voltage protection performance for a non-integrated protection circuit embodiment; and

FIGS. 7A, 7B, and 7C are graphs showing over-voltage protection performance for an integrated protection circuit embodiment comprising an integrated diode bridge and protection circuitry.

DETAILED DESCRIPTION

One aspect of performance in a Power-over-Ethernet (PoE) system is immunity to over-voltage and surge events. The events can be caused by inductive coupling of external lightning events or simply by static electricity buildup on Ethernet cabling. The discharge of energy into sub-micron semiconductor devices can easily become destructive. Typically, expensive and ruggedized external components such as sidactors can be added to shield silicon-based devices from the stresses of external surge events. The external components typically have high capacitance and tend to degrade overall system performance in high speed communication links.

Integrating the diodes and protection circuitry enables a much faster response to a surge event, and hence permits the use of smaller, cheaper, lower voltage components.

Referring to FIG. 3A, a schematic circuit and block diagram illustrates an embodiment of a network device 300 comprising an integrated rectification and protection system 302. The network device 300 comprises a protection circuit 304 configured for coupling to lines 306 between a network connector 308 and an Ethernet physical layer (PHY) 310. The protection circuit 304 comprises a diode bridge 312 and protection circuitry 314 integrated onto a common integrated circuit 316. The word “common” is defined herein as referring to commonality of integration of the diode bridge 312 and the protection circuitry 314 on a single integrated circuit chip 316, and specifically is not used to indicate typical or conventional usage or functionality of the integrated circuit or for any other definition.

The protection circuit 304 can be configured for coupling lines 306 between the network connector 308 and the Ethernet PHY 310 that carry signal and power in a Power-over-Ethernet arrangement.

In the illustrative configuration, the protection circuit diode bridge 312 is coupled to center taps 318 of an Ethernet transformer 320 coupled to the lines 306 between the network connector 308 and the Ethernet PHY 310.

In the illustrative embodiment, the protection circuit 304 can comprise the integrated diode bridge 312 coupled between a supply line 322 and a reference line 324. The integrated protection circuitry 314 is also coupled between the supply line 322 and the reference line 324. A power switch 326 is coupled to the supply line 322 and controlled by the protection circuitry 314.

In the illustrative embodiment, the power switch 326 is depicted as a p-channel power switch Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) that is coupled to the supply line 322 and controlled by the protection circuitry 314.

In some embodiments, for example as shown in FIG. 3A, a Powered Device (PD) controller 328 can be integrated into the protection circuit 304 and coupled between the supply line 322 and the reference line 324.

In some embodiments, the network device 300 can operate on power on the communication line, which is typical in a Power-over-Ethernet (PoE) arrangement. Accordingly, the network device 300 can further comprise a power transformer 330 coupled between the supply line 322 and the reference line 324. One or more capacitors 332 can also be coupled between the supply line 322 and the reference line 324. A switch 334 can be coupled to the reference line 324. For the network device 300 powered by the line, the protection circuit 304 further comprises the integrated diode bridge 312 and the integrated protection circuitry 314 coupled between a supply line 322 and a reference line 324. A power switch 326 is coupled to the supply line 322 and controlled by the protection circuitry 314. A pulse width modulator 336 integrated into the protection circuit 304, coupled between the supply line 322 and the reference line 324, and configured to control the switch 334.

In some embodiments, the network device 300 can operate on power from a wall socket either as a sole power source or in combination with power obtained from the lines. For the network device 300 powered from the wall socket, the protection circuit 304 further comprises a wall jack power source 338 and an Alternating Current (AC) charger 340 coupled to the wall jack power source 338 and coupled between the supply line 322 and the reference line 324. One or more capacitors 342 can also be coupled between the supply line 322 and the reference line 324. A switch 334 can be coupled to the reference line 324. For the network device 300 powered by the wall socket, the protection circuit 304 further comprises the integrated diode bridge 312 and the integrated protection circuitry 314 coupled between a supply line 322 and a reference line 324. A power switch 326 is coupled to the supply line 322 and controlled by the protection circuitry 314.

Referring to FIG. 3B, a schematic circuit and block diagram shows an embodiment of a network device 350 with an integrated rectification and protection system 352 adapted for usage with a T-Less Connect™ solid-state transformer 354. The network device 350 comprises a protection circuit diode bridge 312 coupled to a T-Less Connect™ solid-state transformer 354 coupled to the lines 306 between the network connector 308 and the Ethernet PHY 310. The T-Less Connect™ solid-state transformer 354 functions as a non-magnetic transformer and choke circuit that separates Ethernet signals from power signals, for example by floating ground potential of the Ethernet PHY relative to earth ground.

Referring again to FIG. 3A, in accordance with another embodiment of a network device 300, an integrated circuit 316 configured for coupling to lines 306 between a network connector 308 and an Ethernet physical layer (PHY) 310 comprising a diode bridge 312 and protection circuitry 314 integrated onto a common integrated circuit 316 whereby parasitics in an energy discharge path and stress on the PHY 310 and the diode bridge 312 are reduced.

The network device 300 can further comprise one or more capacitors 342 coupled between the supply line 322 and the reference line 324. The integrated circuit 316 comprises the integrated diode bridge 312 coupled between the supply line 322 and the reference line 324, a p-channel power switch Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) 326 coupled to the supply line 322, and the integrated protection circuitry 314 coupled between the supply line 322 and the reference line 324. The integrated protection circuitry 314 has a rail clamp control line 344 coupled to the p-channel power switch MOSFET 326 that turns on the p-channel power switch MOSFET 326 hard in a surge condition whereby charge is redirected to a capacitor of the one or more capacitors 342.

The protection integrated circuit 316 further includes a driver 346 with an output terminal coupled to the rail clamp control line 344 that drives the gate of the power switch 326. A voltage surge that passes through the diode stack builds a voltage, the driver 346 controls the power switch 326 so that the protection circuitry 314 takes the extra energy and drives the diode bridge 312 harder to reduce the resistance for a short period of time on the power switch 326. For an illustrative example, the power switch may be a 60V or 80V device whereby the voltage between the drain and source is 60V or 80V. The power switch 326 turns on with a voltage of 3-5 volts applied to the gate. In response to an over-voltage surge, the driver 346 can drive the power switch 326 with a voltage applied to the gate of 8-10 volts, turning the power switch 326 on very hard and reducing the on-resistance of the power switch 326, thereby pushing the current through the capacitor 342. In the illustrative embodiment, the power switch 326 is positioned on the positive or source side of the power lines, contrary to more usual positioning of power switches on the ground or negative path. Placement of the power switch 326 on the positive or source path presents a relative size cost since p-channel devices tend to be about 60% slower than n-channel devices. Therefore, in the illustrative embodiment the power switch 326 can be relatively large, for example on the order of twice as large as switches used for similar purposes.

Positioning of the power switch 326 in the positive pathway enables the network device 300 to be grounded at a common earth ground, which can improve performance since an over-voltage surge strikes to ground. Referring to FIG. 3A, the modeled strike path includes a 330Ω resistor that is the strike resistance and a 150 pF capacitor connected to earth ground. The protection integrated circuit 316 couples to the taps of Ethernet transformer 320, connected to the RJ45 connector 308 where the strike passes.

In some embodiments, the network device 300 can comprise one or more capacitors 342 coupled between the supply line 322 and the reference line 324. The integrated circuit 316 comprises the integrated diode bridge 312 and the integrated protection circuitry 314 coupled between the supply line 322 and the reference line 324. A p-channel power switch MOSFET 326 coupled to the supply line. The integrated circuit 316 is configured whereby a high frequency strike short-circuits a capacitor of the capacitor or capacitors 342 and passes to ground.

A current resulting from a surge condition passes through a diode in the integrated diode bridge 312, causing the diode to ring. The current passes out to the tip and through to the power switch 326 to the capacitor 342, for example an 80 nF or 100 nF capacitor. High frequency oscillations applied to the capacitor 342 short-circuit the integrated circuit 304 and drive the high voltage to ground. Accordingly, a high frequency strike is canceled through the capacitor 342 not though any electromagnetic or MOS-based devices, which would be too slow to turn on to address the surge. In comparison to an active device, the capacitor 342 is always active with functionality simply dependent on frequency of applied signals. For example, at DC, the capacitor 342 forms a completely open circuit. At highest frequencies, the capacitor 342 is short-circuited.

In some embodiments, the network device 300 can operate on power either from an Ethernet line or a wall socket. Accordingly, the network device 300 can comprise both a power transformer 330 and a wall jack power source 338 coupled between the supply line 322 and the reference line 324. An AC charger 340 can be coupled to the wall jack power source 338 and coupled between the supply line 322 and the reference line 324. One or more capacitors 342 can also be coupled between the supply line 322 and the reference line 324. A switch 334 can be coupled to the reference line 324. For the network device 300 powered by either the Ethernet line or the wall socket, the integrated circuit 316 further comprises the integrated diode bridge 312 and the integrated protection circuitry 314 coupled between a supply line 322 and a reference line 324. A power switch 326 is integrated into the integrated circuit 316 and coupled to the supply line 322. The power switch 326 is controlled by the protection circuitry 314. A pulse width modulator 336 can be integrated into the integrated circuit 316 and coupled between the supply line 322 and the reference line 324. The pulse width modulator 33 configured to control the switch 334.

Thus, the network device 300, as a Power-over-Ethernet (PoE) device, can operate on power received from the communication lines or from a wall socket. If power is received from the lines, then the entire network device 300 is floating so when hit with a hard ESD discharge or lightning strike the housing holding the device 300 jumps in voltage but has no connection to ground other than a very high impedance path from insulation of the housing to ground. In contrast, when the network device 300 is connected to a wall jack 338, a reference voltage powers the device 300 from a typical AC charger, such as can be used to power a laptop computer. The AC charger has an internal transformer that transforms 110 volts down to 12, 24, or 48 volts and rectifies the voltage. The AC charger also connects a capacitor, for example a 3 nF capacitor, between the output terminal of the charger to ground.

For the network device 300 inside the housing with the AC charger connected to the housing, upon occurrence of a lightning strike a surge passes through a capacitor, for example 300 pF, and a resistor, such as 330Ω, and the capacitor is connected to earth ground. The moment the power switch 326 is turned on to discharge the capacitor, the switch 326 drives the surge through an earth ground capacitor, depicted as 3 nF, which is technically a hard short circuit since the capacitor is very large at 3 nF. Thus, the power switch 326 enables formation of a hard short-circuit to ground without any intervening devices.

When the external AC power adapter is coupled to the device 300, power can also be obtained from another source, such as the communication line. Therefore, a diode 348 is coupled in series with the positive path so that the supply cannot be reversed. Positioning of the n-channel MOSFET power switch 326 and the diode 348 on the positive pathway is contrary to more common switch arrangements which place a switch and diode on the ground pathway. In the event of a lightning strike, the discharge passes through the p-channel power switch 326 and the capacitor 342, then through the ground pathway, through the large 3 nF capacitor 342 and to ground.

Referring again to FIG. 3A, an embodiment of a network device 300 comprises an over-voltage protection integrated circuit 316 that is configured for usage in a Power-over-Ethernet (PoE) application coupling to lines 306 between a network connector 308 and an Ethernet physical layer (PHY) 310. The over-voltage protection integrated circuit 316 comprises a diode bridge 312 and an integrated protection circuitry 314, both integrated into the over-voltage protection integrated circuit 316 and coupled between the supply line 322 and the reference line 324. A power switch 326 is integrated into the over-voltage protection integrated circuit 316 coupled to the supply line 322 and is controlled by the protection circuitry 314. In some embodiments, the power switch 326 can be a p-channel power switch MOSFET.

In some embodiments, the over-voltage protection integrated circuit 316 can further comprise a Powered Device (PD) controller 328 integrated into the over-voltage protection circuit 316 and coupled between the supply line 322 and the reference line 324.

In the illustrative embodiment, the diode bridge 312 coupled to center taps 318 of an Ethernet transformer 320 coupled to the lines between the network connector 308 and the Ethernet PHY 310.

In some embodiments, for example as depicted in FIG. 3B, the diode bridge 312 can be coupled to a T-Less Connect™ solid-state transformer coupled to the lines 306 between the network connector 308 and the Ethernet PHY 354.

Referring to FIGS. 4A and 4B, several schematic flow charts depict embodiments of a method 400 for rectification and surge protection in a Power-over-Ethernet application. As shown in FIG. 4A, the method 400 for over-voltage protection in a network device comprises integrating 402 a diode bridge and protection circuitry into a single or common integrated circuit. A supply line and a reference line are formed 404 in the integrated circuit. The diode bridge and the protection circuitry are coupled 406 between the supply line and the reference line. A power switch is integrated 408 into the common integrated circuit and coupled 410 to the supply line. The power switch is controlled 412 via the protection circuitry.

Referring to FIG. 4B, a method 420 may further comprise actions of coupling 422 the single or common integrated circuit to lines between a network connector and an Ethernet PHY whereby parasitics are reduced 424 in an energy discharge path, reducing 426 stresses on the Ethernet PHY and the diode bridge.

In a typical embodiment, the method can be used to protect against over-voltage in a Power-over-Ethernet (PoE) configuration.

Referring to FIG. 5, a schematic block and circuit diagram illustrates a non-integrated rectification and protection circuit 500. The typical circuit 500 has a discrete breakdown device 514 outside a PD control circuit 528 to clamp the surge voltage and form a large current path for the surge to ground. The discrete breakdown device 514 can be a typical standalone protection circuit. The surge path is around the PD Controller 528, having the disadvantage that key protective components are dependant on board parasitic and layouts which can vary, making consistent performance difficult. In contrast, the network devices 300 and 350 have the diode bridge 312 and protection circuitry 314 integrated along with the PD controller 328 and power switch 326, all of which play a critical role in determining how the high current due to a surge event is discharged.

Lighting strike and large voltage surges are generally modeled as a capacitor charged to a high voltage and then discharged through a resistor. The values of the capacitor (C) and resistor (R) determine the type of energy burst that will occur on the device under test (DUT). If the RC time is small, the currents are generally high and last for a short time frame. If the If the RC time is larger, the currents are generally lower, but last for a longer time frame.

In an illustrative example such as the case of contact discharge, a 150 pf capacitor can be charged to 8000V relative to earth ground and is connected to one of the RJ45 pins via a 330 ohm resistor. Peak discharge currents can be as large as 25 A. In a positive strike on RJ1, Diode 2 (D2) will forward bias and discharge into the clamping circuit through the return path into earth ground. Any parasitic resistance due to the bond wire, skin effect, or board traces significantly increase the voltage spike across the terminals of the protection circuitry. The parasitic resistances Rp1-4 on the contact and board trace, board trace inductances Lp1-2 and the packaged diode bond inductances are modeled in FIG. 5. A wave front time constant of the surge event is typically 6 ns, so that small changes in device reaction time can cause large changes in voltage events.

Referring again to FIG. 5, the protection circuitry 514 and PD controller 528 are typically implemented in ruggedized high voltage circuitry and are less susceptible to over-voltage than the Ethernet PHY 510, which is typically implemented in sensitive, sub-micron process. Hence, the protection circuitry 514 is constructed to absorb most of the charge while developing a small voltage across the PHY terminals and ensuring that the bridge diodes are not subjected to large voltage excursions that exceed specified ratings. Since Power-over-Ethernet operates from a typical 48V supply, voltage excursions are added to the 48V supply, making challenging to remain below the diode reverse bias voltage rating.

As shown in the voltage waveforms depicted in FIG. 6C, after the switch is closed discharging the 8 kV charge into the circuit, a severe ringing in the voltage results across the external bridge diodes than can reach voltages in excess of 120V. Parasitic resistance and inductances largely contribute to the ringing. If board parasitics are higher, a likely possibility since the selected model shown is somewhat optimistic, voltages on the external diodes can rise even higher than 120V. With 25 A surging through the board at high frequencies, for example in a 1 nanosecond wave front, and the combined influence of skin effects, an additional 1Ω resistance can add 25V to the diode voltage.

Referring to FIG. 6A, a graph depicts Voltage Stress waveforms resulting for over-voltage on the discrete circuit shown in FIG. 5. The PHY voltage is approximately 11.5V with some ringing. The internal supplies VDD48 rise up from 48V nominal value to about 54V, voltage at which most external sidactors/surge suppressors are not turned on since the turn-on voltage is approximately 70V. Accordingly, the sidactors/surge suppressors do not supply any protection.

A sidactor becomes operational to protect a circuit at a particular voltage, for example 60 to 72 volts but is susceptible to high frequency strikes in a very fast event lasting about a nanosecond. For example, contact discharge strike of 15000 volts can be so fast that sidactor protection fails, whereby the sidactor does not turn on fast enough and the voltage can shoot high above the specified level, resulting in passage of up to hundreds of volts before sidactor activation. In contrast, a sidactor is effective for protecting against a surge or lightning strike which is much slower and lasts longer than a contact discharge, for example lasting 20 to 40 nanoseconds, due to higher energy, for example imposing a surge in the range of thousands of volts. In response to a surge such as a lightning strike, the sidactors turn on and clamp the voltage to a set maximum such as 72 volts, drawing and dissipating energy from the current path.

Referring to FIG. 6B, a graph depicts Current Stress waveforms in an over-voltage condition on the discrete circuit shown in FIG. 5. In the current waveforms in FIG. 6B, the contact discharge current of approximately 25 A is the strike current surging through the 330Ω resistor once the switch is closed. About 12 Amps flows though the external 80 nF capacitor wherein the total capacitance is 100 nF, with a capacitor C2, for example 20 nF, internal to the PD controller. Approximately 2 Amps flow into the PHY clamp circuit and the power switch M1 which is presumed to be enabled takes 5 Amps.

FIG. 6C, a graph shows Voltage Stress waveforms in an over-voltage condition on the discrete circuit depicted in FIG. 5 including positive and negative strikes. Waveforms indicate positive and negative strikes that place a large stress on the external bridge diodes. Negative strikes are shunted to the ground return path through the diode path D5.

Referring again to FIGS. 3A and 3B in combination with graphs in FIGS. 7A, 7B, and 7C, over-voltage protection performance is shown for the integrated diode bridge 312 and protection circuitry 314 system for comparison to the non-integrated system depicted in FIG. 5 and associated graphs in FIGS. 6A through 6C. As shown in FIGS. 7A, 7B, and 7C, integrating the diode bridge 312 and protection circuitry 314 significantly reduces parasitics in the energy discharge path and reduces stress applied to the PHY 310 and the diode bride 312. The integrated combination enables a lower impedance path for the surge current, thus reducing the voltage build-up with high currents. A 62V rail clamp can also be used turn on the P-Channel Power Switch MOSFET 326 hard thus adding an alternate path for the charge to go through the 4.7 uF capacitor, a path that is more useful in lighting strikes, where the time constants are longer.

The integrated circuit 316 is configured to constrain the maximum possible voltage that can be imposed across the diodes, enabling usage of reasonably-sized diodes while avoiding damage or destruction under conditions of a large voltage surge. Integration of the diode bridge 312 and the protection circuitry 314 substantially eliminates circuit board and bonding package parasitics of the diodes and other components in a non-integrated implementation that is susceptible to very fast transients and contact discharge into a voltage pulse that can cause high frequency ringing at voltages as large as 120 or 150 volts or more, or even 180 to 200 volts for implementations with too close spacing of components.

Integration of the diode bridge 312 and the protection circuitry 314 also can substantially eliminate parasitic oscillations that result from dynamic current changes on circuit traces in a non-integrated implementation and the voltage which rapidly can arise on the traces. The voltage resulting from resistance on the traces can add substantially to the voltage on the line, for example increasing voltage by up to half or more of the line signal, not including ringing or overshoots that can occur due to the inductive nature of the circuit.

FIG. 7A is a graph illustrating Voltage Stress waveforms in an over-voltage condition during operation of the protection circuit 304 including the integrated diode bridge 312 and protection circuitry 314. The integrated design reduces the over-voltage strike stress across input terminals to the diodes by as much as 50%, to about 55V.

FIG. 7B is a graph illustrating Current Stress waveforms in an over-voltage condition during operation of the protection circuit 304 including the integrated diode bridge 312 and protection circuitry 314. As shown in the current waveforms in FIG. 7B, about 13 Amps of the strike current flows though the external capacitor C1, for example an 80 nF capacitor. In the illustrative configuration, the total capacitance is 100 nf with 20 nF internal to the PD controller 328. Approximately 2 Amps flow into the PHY clamp circuit and the power switch M1 takes 5.5 Amps, improving reliability of the PHY 310 under ESD and surge stress events.

FIG. 7C is a graph illustrating Voltage Stress waveforms in an over-voltage condition for positive and negative strikes during operation of the protection circuit 304 including the integrated diode bridge 312 and protection circuitry 314.

In summary, comparing the waveforms in FIGS. 7A through 7C for the integrated protection circuit 304 to waveforms in FIGS. 6A through 6C for a non-integrated system, integrating the diode bridge 312 and protection circuitry 314 significantly increases the reaction time of protection devices and increases PHY immunity to over-voltage stress events. Integrating the components also substantially reduces board-to-board variation and increases overall manufacturability.

As shown in the examples depicted by the graphs, the integrated diode configuration has lower peak diode voltages, for example 57V as compared to 120V. The integrated diode arrangement has lower peak electrostatic discharge (ESD) clamp voltages, shown as 10V in comparison to 11.5V. The integrated diode system has lower ESD clamp currents of 1.8 A compared to 2.6 A. The integrated diode configuration more effectively uses the switch to control excursions, an Iswitch of 5.22 A in comparison to 4.03 A.

The protection circuit 304 with integration of the diode bridge 312 and the protection circuitry 314 is configured whereby high frequency ringing is reduced or eliminated.

Diodes in the diode bridge 512 in the non-integrated implementation propagate high frequency ringing as the non-integrated diodes set up a current through the diodes that tends to be capacitive in behavior. A very high frequency pulse passing through the diode tends to have an inductive behavior, creating even more ringing on the diode. Thus in addition to external parasitic oscillations, inductance also aggravates the ringing. The diodes become inductive and, when inductive, create an even higher ringing. The integrated protection circuit 304 avoids the high frequency ringing of non-integrated diodes which are highly sensitive to surges.

Performance shown in the illustrative examples is expected to be improved even further by implementation of switch gate controls from the Rail clamp.

The illustrative network device 300, the diode bridge 312 and protection circuitry 314 are integrated into the protection circuit 304 at least partly in recognition that for high frequency events, the sidactor used in non-integrated designs does not turn on with sufficient quickness to address various types of over-voltage. The integrated protection circuit 304 is formed to pass current through the circuit as quickly as possible. One aspect of integrated circuit operation is that a high frequency oscillation resulting from an over-voltage condition is canceled by passing through a capacitor. Another aspect of integrated circuit operation is usage of a power switch 326 on the positive or supply side of the integrated circuit 316 that is a relatively large active device.

The IEEE 802.3 Ethernet Standard, which is incorporated herein by reference, addresses loop powering of remote Ethernet devices (802.3af). Power over Ethernet (PoE) standard and other similar standards support standardization of power delivery over Ethernet network cables to power remote client devices through the network connection. The side of link that supplies power is called Powered Supply Equipment (PSE). The side of link that receives power is the Powered device (PD). Other implementations may supply power to network attached devices over alternative networks such as, for example, Home Phoneline Networking alliance (HomePNA) local area networks and other similar networks. HomePNA uses existing telephone wires to share a single network connection within a home or building. In other examples, devices may support communication of network data signals over power lines.

In various configurations described herein, a magnetic transformer of conventional systems may be eliminated while transformer functionality is maintained. Techniques enabling replacement of the transformer may be implemented in the form of integrated circuits (ICs) or discrete components.

FIG. 1A is a schematic block diagram that illustrates a high level example embodiment of devices in which power is supplied separately to network attached client devices 112 through 116 that may benefit from receiving power and data via the network connection. The devices are serviced by a local area network (LAN) switch 110 for data. Individual client devices 112 through 116 have separate power connections 118 to electrical outlets 120. FIG. 1B is a schematic block diagram that depicts a high level example embodiment of devices wherein a switch 110 is a power supply equipment (PSE)-capable power-over Ethernet (PoE) enabled LAN switch that supplies both data and power signals to client devices 112 through 116. Network attached devices may include a Voice Over Internet Protocol (VOIP) telephone 112, access points, routers, gateways 114 and/or security cameras 116, as well as other known network appliances. Network supplied power enables client devices 112 through 116 to eliminate power connections 118 to electrical outlets 120 as shown in FIG. 1A. Eliminating the second connection enables the network attached device to have greater reliability when attached to the network with reduced cost and facilitated deployment.

Although the description herein may focus and describe a system and method for coupling high bandwidth data signals and power distribution between the integrated circuit and cable that uses transformer-less ICs with particular detail to the IEEE 802.3af Ethernet standard, the concepts may be applied in non-Ethernet applications and non-IEEE 802.3af applications. Also, the concepts may be applied in subsequent standards that supersede or complement the IEEE 802.3af standard.

Various embodiments of the depicted system may support solid state, and thus non-magnetic, transformer circuits operable to couple high bandwidth data signals and power signals with new mixed-signal IC technology, enabling elimination of cumbersome, real-estate intensive magnetic-based transformers.

Typical conventional communication systems use transformers to perform common mode signal blocking, 1500 volt isolation, and AC coupling of a differential signature as well as residual lightning or electromagnetic shock protection. The functions are replaced by a solid state or other similar circuits in accordance with embodiments of circuits and systems described herein whereby the circuit may couple directly to the line and provide high differential impedance and low common mode impedance. High differential impedance enables separation of the physical layer (PHY) signal from the power signal. Low common mode impedance enables elimination of a choke, allowing power to be tapped from the line. The local ground plane may float to eliminate a requirement for 1500 volt isolation. Additionally, through a combination of circuit techniques and lightning protection circuitry, voltage spike or lightning protection can be supplied to the network attached device, eliminating another function performed by transformers in traditional systems or arrangements. The disclosed technology may be applied anywhere transformers are used and is not limited to Ethernet applications.

Specific embodiments of the circuits and systems disclosed herein may be applied to various powered network attached devices or Ethernet network appliances. Such appliances include, but are not limited to VoIP telephones, routers, printers, and other similar devices.

Referring to FIG. 2, a functional block diagram depicts an embodiment of a network device 200 including a T-Less Connect™ solid-state transformer. The illustrative network device comprises a power potential rectifier 202 adapted to conductively couple a network connector 232 to an integrated circuit 270, 272 that rectifies and passes a power signal and data signal received from the network connector 232. The power potential rectifier 202 regulates a received power and/or data signal to ensure proper signal polarity is applied to the integrated circuit 270, 272.

The network device 200 is shown with the power sourcing switch 270 sourcing power through lines 1 and 2 of the network connector 232 in combination with lines 3 and 6.

In some embodiments, the power potential rectifier 202 is configured to couple directly to lines of the network connector 232 and regulate the power signal whereby the power potential rectifier 202 passes the data signal with substantially no degradation.

In some configuration embodiments, the network connector 232 receives multiple twisted pair conductors 204, for example twisted 22-26 gauge wire. Any one of a subset of the twisted pair conductors 204 can forward bias to deliver current and the power potential rectifier 202 can forward bias a return current path via a remaining conductor of the subset.

FIG. 2 illustrates the network interface 200 including a network powered device (PD) interface and a network power supply equipment (PSE) interface, each implementing a non-magnetic transformer and choke circuitry. A powered end station 272 is a network interface that includes a network connector 232, non-magnetic transformer and choke power feed circuitry 262, a network physical layer 236, and a power converter 238. Functionality of a magnetic transformer is replaced by circuitry 262. In the context of an Ethernet network interface, network connector 232 may be a RJ45 connector that is operable to receive multiple twisted wire pairs. Protection and conditioning circuitry may be located between network connector 232 and non-magnetic transformer and choke power feed circuitry 262 to attain surge protection in the form of voltage spike protection, lighting protection, external shock protection or other similar active functions. Conditioning circuitry may be a diode bridge or other rectifying component or device. A bridge or rectifier may couple to individual conductive lines 1-8 contained within the RJ45 connector. The circuits may be discrete components or an integrated circuit within non-magnetic transformer and choke power feed circuitry 262.

In an Ethernet application, the IEEE 802.3af standard (PoE standard) enables delivery of power over Ethernet cables to remotely power devices. The portion of the connection that receives the power may be referred to as the powered device (PD). The side of the link that supplies power is called the power sourcing equipment (PSE).

In the powered end station 272, conductors 1 through 8 of the network connector 232 couple to non-magnetic transformer and choke power feed circuitry 262. Non-magnetic transformer and choke power feed circuitry 262 may use the power feed circuit and separate the data signal portion from the power signal portion. The data signal portion may then be passed to the network physical layer (PHY) 236 while the power signal passes to power converter 238.

If the powered end station 272 is used to couple the network attached device or PD to an Ethernet network, network physical layer 236 may be operable to implement the 10 Mbps, 100 Mbps, and/or 1 Gbps physical layer functions as well as other Ethernet data protocols that may arise. The Ethernet PHY 236 may additionally couple to an Ethernet media access controller (MAC). The Ethernet PHY 236 and Ethernet MAC when coupled are operable to implement the hardware layers of an Ethernet protocol stack. The architecture may also be applied to other networks. If a power signal is not received but a traditional, non-power Ethernet signal is received the nonmagnetic power feed circuitry 262 still passes the data signal to the network PHY.

The power signal separated from the network signal within non-magnetic transformer and choke power feed circuit 262 by the power feed circuit is supplied to power converter 238. Typically the power signal received does not exceed 57 volts SELV (Safety Extra Low Voltage). Typical voltage in an Ethernet application is 48-volt power. Power converter 238 may then further transform the power as a DC to DC converter to provide 1.8 to 3.3 volts, or other voltages specified by many Ethernet network attached devices.

Power-sourcing switch 270 includes a network connector 232, Ethernet or network physical layer 254, PSE controller 256, non-magnetic transformer and choke power supply circuitry 266, and possibly a multiple-port switch. Transformer functionality is supplied by non-magnetic transformer and choke power supply circuitry 266. Power-sourcing switch 270 may be used to supply power to network attached devices. Powered end station 272 and power sourcing switch 270 may be applied to an Ethernet application or other network-based applications such as, but not limited to, a vehicle-based network such as those found in an automobile, aircraft, mass transit system, or other like vehicle. Examples of specific vehicle-based networks may include a local interconnect network (LIN), a controller area network (CAN), or a flex ray network. All may be applied specifically to automotive networks for the distribution of power and data within the automobile to various monitoring circuits or for the distribution and powering of entertainment devices, such as entertainment systems, video and audio entertainment systems often found in today's vehicles. Other networks may include a high speed data network, low speed data network, time-triggered communication on CAN (TTCAN) network, a J1939-compliant network, ISO11898-compliant network, an ISO11519-2-compliant network, as well as other similar networks. Other embodiments may supply power to network attached devices over alternative networks such as but not limited to a HomePNA local area network and other similar networks. HomePNA uses existing telephone wires to share a single network connection within a home or building. Alternatively, embodiments may be applied where network data signals are provided over power lines.

Non-magnetic transformer and choke power feed circuitry 262 and 266 enable elimination of magnetic transformers with integrated system solutions that enable an increase in system density by replacing magnetic transformers with solid state power feed circuitry in the form of an integrated circuit or discreet component.

In some embodiments, non-magnetic transformer and choke power feed circuitry 262, network physical layer 236, power distribution management circuitry 254, and power converter 238 may be integrated into a single integrated circuit rather than discrete components at the printed circuit board level. Optional protection and power conditioning circuitry may be used to interface the integrated circuit to the network connector 232.

The Ethernet PHY may support the 10/100/1000 Mbps data rate and other future data networks such as a 10000 Mbps Ethernet network. Non-magnetic transformer and choke power feed circuitry 262 supplies line power minus the insertion loss directly to power converter 238, converting power first to a 12V supply then subsequently to lower supply levels. The circuit may be implemented in any appropriate process, for example a 0.18 or 0.13 micron process or any suitable size process.

Non-magnetic transformer and choke power feed circuitry 262 may implement functions including IEEE 802.3.af signaling and load compliance, local unregulated supply generation with surge current protection, and signal transfer between the line and integrated Ethernet PHY. Since devices are directly connected to the line, the circuit may be implemented to withstand a secondary lightning surge.

For the power over Ethernet (PoE) to be IEEE 802.3af standard compliant, the PoE may be configured to accept power with various power feeding schemes and handle power polarity reversal. A rectifier, such as a diode bridge, a switching network, or other circuit, may be implemented to ensure power signals having an appropriate polarity are delivered to nodes of the power feed circuit. Any one of the conductors 1, 4, 7 or 3 of the network RJ45 connection can forward bias to deliver current and any one of the return diodes connected can forward bias to form a return current path via one of the remaining conductors. Conductors 2, 5, 8 and 4 are connected similarly.

Non-magnetic transformer and choke power feed circuitry 262 applied to PSE may take the form of a single or multiple port switch to supply power to single or multiple devices attached to the network. Power sourcing switch 270 may be operable to receive power and data signals and combine to communicate power signals which are then distributed via an attached network. If power sourcing switch 270 is a gateway or router, a high-speed uplink couples to a network such as an Ethernet network or other network. The data signal is relayed via network PHY 254 and supplied to non-magnetic transformer and choke power feed circuitry 266. PSE switch 270 may be attached to an AC power supply or other internal or external power supply to supply a power signal to be distributed to network-attached devices that couple to power sourcing switch 270. Power controller 256 within or coupled to non-magnetic transformer and choke power feed circuitry 266 may determine, in accordance with IEEE standard 802.3af, whether a network-attached device in the case of an Ethernet network-attached device is a device operable to receive power from power supply equipment. When determined that an IEEE 802.3af compliant powered device (PD) is attached to the network, power controller 256 may supply power from power supply to non-magnetic transformer and choke power feed circuitry 266, which is sent to the downstream network-attached device through network connectors, which in the case of the Ethernet network may be an RJ45 receptacle and cable.

IEEE 802.3af Standard is to fully comply with existing non-line powered Ethernet network systems. Accordingly, PSE detects via a well-defined procedure whether the far end is PoE compliant and classify sufficient power prior to applying power to the system. Maximum allowed voltage is 57 volts for compliance with SELV (Safety Extra Low Voltage) limits.

For backward compatibility with non-powered systems, applied DC voltage begins at a very low voltage and only begins to deliver power after confirmation that a PoE device is present. In the classification phase, the PSE applies a voltage between 14.5V and 20.5V, measures the current and determines the power class of the device. In one embodiment the current signature is applied for voltages above 12.5V and below 23 Volts. Current signature range is 0-44 mA.

The normal powering mode is switched on when the PSE voltage crosses 42 Volts where power MOSFETs are enabled and the large bypass capacitor begins to charge.

A maintain power signature is applied in the PoE signature block—a minimum of 10 mA and a maximum of 23.5 kohms may be applied for the PSE to continue to feed power. The maximum current allowed is limited by the power class of the device (class 0-3 are defined). For class 0, 12.95 W is the maximum power dissipation allowed and 400 ma is the maximum peak current. Once activated, the PoE will shut down if the applied voltage falls below 30V and disconnect the power MOSFETs from the line.

Power feed devices in normal power mode provide a differential open circuit at the Ethernet signal frequencies and a differential short at lower frequencies. The common mode circuit presents the capacitive and power management load at frequencies determined by the gate control circuit.

Terms “substantially”, “essentially”, or “approximately”, that may be used herein, relate to an industry-accepted tolerance to the corresponding term. Such an industry-accepted tolerance ranges from less than one percent to twenty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. The term “coupled”, as may be used herein, includes direct coupling and indirect coupling via another component, element, circuit, or module where, for indirect coupling, the intervening component, element, circuit, or module does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. Inferred coupling, for example where one element is coupled to another element by inference, includes direct and indirect coupling between two elements in the same manner as “coupled”.

While the present disclosure describes various embodiments, these embodiments are to be understood as illustrative and do not limit the claim scope. Many variations, modifications, additions and improvements of the described embodiments are possible. For example, those having ordinary skill in the art will readily implement the steps necessary to provide the structures and methods disclosed herein, and will understand that the process parameters, materials, and dimensions are given by way of example only. The parameters, materials, and dimensions can be varied to achieve the desired structure as well as modifications, which are within the scope of the claims. Variations and modifications of the embodiments disclosed herein may also be made while remaining within the scope of the following claims. For example, various aspects or portions of a network interface are described including several optional implementations for particular portions. Any suitable combination or permutation of the disclosed designs may be implemented. 

1. A network device comprising: a protection circuit configured for coupling to lines between a network connector and an Ethernet physical layer (PHY), the protection circuit comprising a diode bridge and protection circuitry integrated onto a common integrated circuit.
 2. The network device according to claim 1 further comprising: the protection circuit configured for coupling lines between the network connector and the Ethernet physical layer (PHY) that carry signal and power in a Power-over-Ethernet arrangement.
 3. The network device according to claim 1 further comprising: the protection circuit diode bridge coupled to center taps of an Ethernet transformer coupled to the lines between the network connector and the Ethernet physical layer (PHY).
 4. The network device according to claim 1 further comprising: the protection circuit diode bridge coupled to a T-Less Connect™ solid-state transformer coupled to the lines between the network connector and the Ethernet physical layer (PHY).
 5. The network device according to claim 1 further comprising: the protection circuit comprising: the integrated diode bridge coupled between a supply line and a reference line; the integrated protection circuitry coupled between the supply line and the reference line; and a power switch coupled to the supply line and controlled by the protection circuitry.
 6. The network device according to claim 1 further comprising: the protection circuit comprising: the integrated diode bridge coupled between a supply line and a reference line; the integrated protection circuitry coupled between the supply line and the reference line; and a p-channel power switch Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) coupled to the supply line and controlled by the protection circuitry.
 7. The network device according to claim 1 further comprising: the protection circuit comprising: the integrated diode bridge coupled between a supply line and a reference line; the integrated protection circuitry coupled between the supply line and the reference line; a power switch integrated into the protection circuit and coupled to the supply line and controlled by the protection circuitry; and a Powered Device (PD) controller integrated into the protection circuit and coupled between the supply line and the reference line.
 8. The network device according to claim 1 further comprising: a power transformer coupled between a supply line and a reference line; at least one capacitor coupled between the supply line and the reference line; a switch coupled to the reference line; and the protection circuit comprising: the integrated diode bridge coupled between the supply line and the reference line; the integrated protection circuitry coupled between the supply line and the reference line; a power switch integrated into the protection circuit and coupled to the supply line and controlled by the protection circuitry; and a pulse width modulator integrated into the protection circuit, coupled between the supply line and the reference line, and configured to control the switch.
 9. The network device according to claim 1 further comprising: a wall jack power source; an Alternating Current (AC) charger coupled to the wall jack power source and coupled between a supply line and a reference line; at least one capacitor coupled between the supply line and the reference line; a switch coupled to the reference line; and the protection circuit comprising: the integrated diode bridge coupled between the supply line and the reference line; the integrated protection circuitry coupled between the supply line and the reference line; and a power switch integrated into the protection circuit and coupled to the supply line and controlled by the protection circuitry.
 10. A network device comprising: an integrated circuit configured for coupling to lines between a network connector and an Ethernet physical layer (PHY) and comprising a diode bridge and protection circuitry integrated onto a common integrated circuit whereby parasitics in an energy discharge path and stress on the PHY and the diode bridge are reduced.
 11. The network device according to claim 10 further comprising: at least one capacitor coupled between a supply line and a reference line; and the integrated circuit comprising: the integrated diode bridge coupled between the supply line and the reference line; a p-channel power switch Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) coupled to the supply line; and the integrated protection circuitry coupled between the supply line and the reference line, and having a rail clamp control line coupled to the p-channel power switch MOSFET that turns on the p-channel power switch MOSFET hard in a surge condition whereby charge is redirected to a capacitor of the at least one capacitor.
 12. The network device according to claim 10 further comprising: at least one capacitor coupled between a supply line and a reference line; and the integrated circuit comprising: the integrated diode bridge coupled between the supply line and the reference line; a p-channel power switch Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) coupled to the supply line; and the integrated protection circuitry coupled between the supply line and the reference line, the integrated circuit configured whereby a high frequency strike short-circuits a capacitor of the at least one capacitor and passes to ground.
 13. The network device according to claim 10 further comprising: a power transformer coupled between a supply line and a reference line; a wall jack power source; an Alternating Current (AC) charger coupled to the wall jack power source and coupled between a supply line and a reference line; at least one capacitor coupled between the supply line and the reference line; a switch coupled to the reference line; and the integrated circuit comprising: the integrated diode bridge coupled between the supply line and the reference line; the integrated protection circuitry coupled between the supply line and the reference line; a power switch integrated into the integrated circuit and coupled to the supply line and controlled by the protection circuitry; and a pulse width modulator integrated into the integrated circuit, coupled between the supply line and the reference line, and configured to control the switch.
 14. A network device comprising: an over-voltage protection integrated circuit configured for usage in a Power-over-Ethernet (PoE) application coupling to lines between a network connector and an Ethernet physical layer (PHY) comprising: a diode bridge integrated into the over-voltage protection integrated circuit coupled between a supply line and a reference line; a integrated protection circuitry integrated into the over-voltage protection integrated circuit coupled between the supply line and the reference line; and a power switch integrated into the over-voltage protection integrated circuit coupled to the supply line and controlled by the protection circuitry.
 15. The network device according to claim 14 wherein: the power switch is a p-channel power switch Metal Oxide Semiconductor Field-Effect Transistor (MOSFET).
 16. The network device according to claim 14 further comprising: the over-voltage protection integrated circuit further comprising: a Powered Device (PD) controller integrated into the over-voltage protection circuit and coupled between the supply line and the reference line.
 17. The network device according to claim 14 further comprising: the diode bridge coupled to center taps of an Ethernet transformer coupled to the lines between the network connector and the Ethernet physical layer (PHY).
 18. The network device according to claim 14 further comprising: the diode bridge coupled to a T-Less Connect™ solid-state transformer coupled to the lines between the network connector and the Ethernet physical layer (PHY).
 19. A method for over-voltage protection in a network device comprising: integrating a diode bridge and protection circuitry into a common integrated circuit; forming a supply line and a reference line in the integrated circuit; coupling the diode bridge and the protection circuitry between the supply line and the reference line; integrating a power switch into the common integrated circuit; coupling the power switch to the supply line; and controlling the power switch via the protection circuitry.
 20. The method according to claim 19 further comprising: coupling the common integrated circuit to lines between a network connector and an Ethernet physical layer (PHY); and reducing parasitics in an energy discharge path; reducing stress on the Ethernet physical layer (PHY) and the diode bridge.
 21. The method according to claim 19 further comprising: protecting against over-voltage in a Power-over-Ethernet (PoE) configuration. 